1
|
Buschmann E, Van Steenkiste G, Duytschaever M, Segers P, Ibrahim L, van Loon G, Decloedt A. In vitro characterization of radiofrequency ablation lesions in equine and swine myocardial tissue. Sci Rep 2024; 14:22877. [PMID: 39358479 PMCID: PMC11447003 DOI: 10.1038/s41598-024-74486-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2024] [Accepted: 09/26/2024] [Indexed: 10/04/2024] Open
Abstract
Radiofrequency ablation is a promising technique for arrhythmia treatment in horses. Due to the thicker myocardial wall and higher blood flow in horses, it is unknown if conventional radiofrequency settings used in human medicine can be extrapolated to horses. The study aim is to describe the effect of ablation settings on lesion dimensions in equine myocardium. To study species dependent effects, results were compared to swine myocardium. Right ventricular and right and left atrial equine myocardium and right ventricular swine myocardium were suspended in a bath with circulating isotonic saline at 37 °C. The ablation catheter delivered radiofrequency energy at different-power-duration combinations with a contact force of 20 g. Lesion depth and width were measured and lesion volume was calculated. Higher power or longer duration of radiofrequency energy delivery increased lesion size significantly in the equine atrial myocardium and in equine and swine ventricular myocardium (P < 0.001). Mean lesion depth in equine atrial myocardium ranged from 2.9 to 5.5 mm with a diameter ranging from 6.9 to 10.1 mm. Lesion diameter was significantly larger in equine tissue compared to swine tissue (P = 0.020). Obtained data in combination with estimated wall thickness can improve lesion transmurality which might reduce arrhythmia recurrence. Optimal ablation settings may differ between species.
Collapse
Affiliation(s)
- Eva Buschmann
- Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Equine Cardioteam Ghent University, Ghent University, Merelbeke, Belgium.
| | - Glenn Van Steenkiste
- Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Equine Cardioteam Ghent University, Ghent University, Merelbeke, Belgium
| | | | - Patrick Segers
- Institute of Biomedical Engineering and Technology, Faculty of Engineering and Architecture, Ghent University, Ghent, Belgium
| | - Lara Ibrahim
- Department of Morphology, Imaging, Orthopedics, Rehabilitation and Nutrition, Ghent University, Merelbeke, Belgium
| | - Gunther van Loon
- Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Equine Cardioteam Ghent University, Ghent University, Merelbeke, Belgium
| | - Annelies Decloedt
- Department of Internal Medicine, Reproduction and Population Medicine, Faculty of Veterinary Medicine, Equine Cardioteam Ghent University, Ghent University, Merelbeke, Belgium
| |
Collapse
|
2
|
Wang Z, Liang M, Sun J, Zhang J, Li Y, Xu L, Han Y. Epicardial pulsed-field ablation-impact of electric field and heat distribution induced by coronary metallic stents. Front Cardiovasc Med 2024; 11:1445424. [PMID: 39267803 PMCID: PMC11391106 DOI: 10.3389/fcvm.2024.1445424] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2024] [Accepted: 08/13/2024] [Indexed: 09/15/2024] Open
Abstract
Background Pulsed-field ablation (PFA) technique is a nonthermal ablation technique. No study has yet evaluated the effect of the positional relationship between the ablation electrode (AE) and the coronary metal stent (CMS) on the electric field distribution and temperature distribution in epicardial ablation. Our study aimed to evaluate the effect of the CMS on the electric field as well as the temperature distribution in different models. Methods Multi-angle modeling of the CMS and AE was performed. The PFA ablation region was evaluated with a field strength contour of 1,000 V/cm, which was used to assess the validity of the two-dimensional (2D) model simulation data as well as the distribution of the multi-angle electric field and temperature in the three-dimensional (3D) model. Results The presence of the CMS had little effect on the width of the ablation area (0.2 mm). In the 3D model, the temperature of the ablation area was highest when the angle between the AE and the CMS was in the 90° position (43.4°C, 41.3°C); a change in the distance between the AE and the CMS affected the temperature of the ablation area (maximum 2.1°C) and the width of the ablation (maximum 0.32 mm). Conclusion The presence of the CMS distorts the distribution of the electric field, but does not produce a change in the extent of the ablation damage, nor does it bring thermal damage to the ablation region. Different simulation models give similar results in PFA calculations, and this study effectively reduces the complexity of modeling simulation.
Collapse
Affiliation(s)
- Zhen Wang
- College of Medicine and Biological Information Engineering, Northeastern University, Shenyang, China
- Department of Cardiology, General Hospital of Northern Theater Command, Shenyang, China
| | - Ming Liang
- Department of Cardiology, General Hospital of Northern Theater Command, Shenyang, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases, General Hospital of Northern Theater Command, Shenyang, China
| | - Jingyang Sun
- Department of Cardiology, General Hospital of Northern Theater Command, Shenyang, China
| | - Jie Zhang
- Department of Cardiology, General Hospital of Northern Theater Command, Shenyang, China
| | - Yunhao Li
- Department of Cardiology, General Hospital of Northern Theater Command, Shenyang, China
- Graduate School of China Medical University, China Medical University, Shenyang, China
| | - Lisheng Xu
- College of Medicine and Biological Information Engineering, Northeastern University, Shenyang, China
| | - Yaling Han
- Department of Cardiology, General Hospital of Northern Theater Command, Shenyang, China
- National Key Laboratory of Frigid Zone Cardiovascular Diseases, General Hospital of Northern Theater Command, Shenyang, China
| |
Collapse
|
3
|
Estevez-Laborí F, O'Brien B, González-Suárez A. Difference between endocardial and epicardial application of pulsed fields for targeting Epicardial Ganglia: An in-silico modelling study. Comput Biol Med 2024; 174:108490. [PMID: 38642490 DOI: 10.1016/j.compbiomed.2024.108490] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 04/04/2024] [Accepted: 04/15/2024] [Indexed: 04/22/2024]
Abstract
BACKGROUND Pulsed Field Ablation (PFA) has recently been proposed as a non-thermal energy to treat atrial fibrillation by selective ablation of ganglionated plexi (GP) embedded in epicardial fat. While some of PFA-technologies use an endocardial approach, others use epicardial access with promising pre-clinical results. However, as each technology uses a different and sometimes proprietary pulse application protocol, the comparation between endocardial vs. epicardial approach is almost impossible in experimental terms. For this reason, our study, based on a computational model, allows a direct comparison of electric field distribution and thermal-side effects of both approaches under equal conditions in terms of electrode design, pulse protocol and anatomical characteristics of the tissues involved. METHODS 2D computational models with axial symmetry were built for endocardial and epicardial approaches. Atrial (1.5-2.5 mm) and fat (1-5 mm) thicknesses were varied to simulate a representative sample of what happens during PFA ablation for different applied voltage values (1000, 1500 and 2000 V) and number of pulses (30 and 50). RESULTS The epicardial approach was superior for capturing greater volumes of fat when the applied voltage was increased: 231 mm3/kV with the epicardial approach vs. 182 mm3/kV with the endocardial approach. In relation to collateral damage to the myocardium, the epicardial approach considerably spares the myocardium, unlike what happens with the endocardial approach. Although the epicardial approach caused much more thermal damage in the fat, there is not a significant difference between the approaches in terms of size of thermal damage in the myocardium. CONCLUSIONS Our results suggest that epicardial PFA ablation of GPs is more effective than an endocardial approach. The proximity and directionality of the electric field deposited using an epicardial approach are key to ensuring that higher electric field strengths and increased temperatures are obtained within the epicardial fat, thus contributing to selective ablation of the GPs with minimal myocardial damage.
Collapse
Affiliation(s)
| | | | - Ana González-Suárez
- Translational Medical Device Lab, School of Medicine, University of Galway, Ireland; IBIO, Escuela Superior de Ingeniería, Ciencia y Tecnología, Universidad Internacional de Valencia, Valencia, Spain.
| |
Collapse
|
4
|
Nussinovitch U, Wang P, Babakhanian M, Narayan SM, Viswanathan M, Badhwar N, Zheng L, Sauer WH, Nguyen DT. Ambient circulation surrounding an ablation catheter tip affects ablation lesion characteristics. J Cardiovasc Electrophysiol 2023; 34:918-927. [PMID: 36852908 PMCID: PMC10115146 DOI: 10.1111/jce.15874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2022] [Revised: 02/01/2023] [Accepted: 02/18/2023] [Indexed: 03/01/2023]
Abstract
INTRODUCTION The association between ambient circulating environments (CEs) and ablation lesions has been largely underexplored. METHODS Viable bovine myocardium was placed in a saline bath in an ex vivo endocardial model. Radiofrequency (RF) ablation was performed using three different ablation catheters: 3.5 mm open irrigated (OI), 4, and 8 mm. Variable flow rates of surrounding bath fluids were applied to simulate standard flow, high flow, and no flow. For in vivo epicardial ablation, 24 rats underwent a single OI ablation and performed with circulating saline (30 ml/min; n = 12), versus those immersed in saline without circulation (n = 12). RESULTS High flow reduced ablation lesion volumes for all three catheters. In no-flow endocardial CE, both 4 mm and OI catheters produced smaller lesions compared with standard flow. However, the 8 mm catheter produced the largest lesions in a no-flow CE. Ablation performed in an in vivo model with CE resulted in smaller lesions compared with ablation performed in a no-flow environment. No statistically significant differences in steam pops were found among the groups. CONCLUSION A higher endocardial CE flow can decrease RF effectiveness. Cardiac tissue subjected to no endocardial CE flow may also limit RF for 4 mm catheters, but not for OI catheters; these findings may have implications for RF ablation safety and efficacy, especially in the epicardial space without circulating fluid or in the endocardium under varying flow conditions.
Collapse
Affiliation(s)
- Udi Nussinovitch
- Section of Cardiac Electrophysiology, Division of Cardiovascular Medicine, Stanford University, Stanford, California, USA
| | - Paul Wang
- Section of Cardiac Electrophysiology, Division of Cardiovascular Medicine, Stanford University, Stanford, California, USA
| | - Meghedi Babakhanian
- Section of Cardiac Electrophysiology, Division of Cardiovascular Medicine, Stanford University, Stanford, California, USA
| | - Sanjiv M. Narayan
- Section of Cardiac Electrophysiology, Division of Cardiovascular Medicine, Stanford University, Stanford, California, USA
| | - Mohan Viswanathan
- Section of Cardiac Electrophysiology, Division of Cardiovascular Medicine, Stanford University, Stanford, California, USA
| | - Nitish Badhwar
- Section of Cardiac Electrophysiology, Division of Cardiovascular Medicine, Stanford University, Stanford, California, USA
| | - Lijun Zheng
- Section of Cardiac Electrophysiology, Division of Cardiology, University of Colorado, Aurora, Colorado, USA
| | - William H. Sauer
- Section of Cardiac Electrophysiology, Division of Cardiology, Brigham and Women’s Hospital, Boston, Massachusetts, USA
| | - Duy T. Nguyen
- Section of Cardiac Electrophysiology, Division of Cardiovascular Medicine, Stanford University, Stanford, California, USA
| |
Collapse
|
5
|
Effects of Pulsed Radiofrequency Source on Cardiac Ablation. Bioengineering (Basel) 2023; 10:bioengineering10020227. [PMID: 36829721 PMCID: PMC9952521 DOI: 10.3390/bioengineering10020227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 01/30/2023] [Accepted: 02/03/2023] [Indexed: 02/10/2023] Open
Abstract
Heart arrhythmia is caused by abnormal electrical conduction through the myocardium, which in some cases, can be treated with heat. One of the challenges is to reduce temperature peaks-by still guaranteeing an efficient treatment where desired-to avoid any healthy tissue damage or any electrical issues within the device employed. A solution might be employing pulsed heat, in which thermal dose is given to the tissue with a variation in time. In this work, pulsed heat is used to modulate induced temperature fields during radiofrequency cardiac ablation. A three-dimensional model of the myocardium, catheter and blood flow is developed. Porous media, heat conduction and Navier-Stokes equations are, respectively, employed for each of the investigated domains. For the electric field, solved via Laplace equation, it is assumed that the electrode is at a fixed voltage. Pulsed heating effects are considered with a cosine time-variable pulsed function for the fixed voltage by constraining the product between this variable and time. Different dimensionless frequencies are considered and applied for different blood flow velocity and sustained voltages. Results are presented for different pulsed conditions to establish if a reasonable ablation zone, known from the obtained temperature profiles, can be obtained without any undesired temperature peaks.
Collapse
|
6
|
González-Suárez A, Pérez JJ, O’Brien B, Elahi A. In Silico Modelling to Assess the Electrical and Thermal Disturbance Provoked by a Metal Intracoronary Stent during Epicardial Pulsed Electric Field Ablation. J Cardiovasc Dev Dis 2022; 9:jcdd9120458. [PMID: 36547455 PMCID: PMC9784210 DOI: 10.3390/jcdd9120458] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2022] [Revised: 12/07/2022] [Accepted: 12/12/2022] [Indexed: 12/15/2022] Open
Abstract
Background: Pulsed Electric Field (PEF) ablation has been recently proposed to ablate cardiac ganglionic plexi (GP) aimed to treat atrial fibrillation. The effect of metal intracoronary stents in the vicinity of the ablation electrode has not been yet assessed. Methods: A 2D numerical model was developed accounting for the different tissues involved in PEF ablation with an irrigated ablation device. A coronary artery (with and without a metal intracoronary stent) was considered near the ablation source (0.25 and 1 mm separation). The 1000 V/cm threshold was used to estimate the ‘PEF-zone’. Results: The presence of the coronary artery (with or without stent) distorts the E-field distribution, creating hot spots (higher E-field values) in the front and rear of the artery, and cold spots (lower E-field values) on the sides of the artery. The value of the E-field inside the coronary artery is very low (~200 V/cm), and almost zero with a metal stent. Despite this distortion, the PEF-zone contour is almost identical with and without artery/stent, remaining almost completely confined within the fat layer in any case. The mentioned hot spots of E-field translate into a moderate temperature increase (<48 °C) in the area between the artery and electrode. These thermal side effects are similar for pulse intervals of 10 and 100 μs. Conclusions: The presence of a metal intracoronary stent near the ablation device during PEF ablation simply ‘amplifies’ the E-field distortion already caused by the presence of the vessel. This distortion may involve moderate heating (<48 °C) in the tissue between the artery and ablation electrode without associated thermal damage.
Collapse
Affiliation(s)
- Ana González-Suárez
- School of Engineering, University of Galway, H91 TK33 Galway, Ireland
- Translational Medical Device Lab, University of Galway, H91 YR71 Galway, Ireland
- Correspondence:
| | - Juan J. Pérez
- BioMIT, Department of Electronic Engineering, Universitat Politècnica de València, 46022 Valencia, Spain
| | - Barry O’Brien
- AtriAN Medical Limited, Unit 204, University of Galway Business Innovation Centre, Upper Newcastle, H91 W60E Galway, Ireland
| | - Adnan Elahi
- School of Engineering, University of Galway, H91 TK33 Galway, Ireland
- Translational Medical Device Lab, University of Galway, H91 YR71 Galway, Ireland
| |
Collapse
|
7
|
Sánchez-Muñoz EJ, Berjano E, González-Suárez A. Computer simulations of consecutive radiofrequency pulses applied at the same point during cardiac catheter ablation: Implications for lesion size and risk of overheating. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 220:106817. [PMID: 35468542 DOI: 10.1016/j.cmpb.2022.106817] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 04/12/2022] [Accepted: 04/14/2022] [Indexed: 06/14/2023]
Abstract
BACKGROUND AND OBJECTIVES To study temperature distribution and lesion size during two repeated radiofrequency (RF) pulses applied at the same point in the context of RF cardiac ablation (RFCA). METHODS An in-silico RFCA model accounting for reversible and irreversible changes in myocardium electrical properties due to RF-induced heating. Arrhenius damage model to estimate lesion size during the application of two 20 W pulses at intervals (INT) of from 5 to 70 s. We considered two pulse durations: 20 s and 30 s. RESULTS INT has a significant effect on lesion size and maximum tissue temperature (TMAX). The shorter the INT the greater the increase in lesion size after the second pulse but also the greater the TMAX. If the second pulse is applied almost immediately (INT=5 s), depth increases 1.4 mm and 1.5 mm for pulses of 20 s and 30 s, respectively. If INT is longer than 30 s it increases 1.1 mm and 1.3 mm for pulses of 20 s and 30 s, respectively. While a single 20 s pulse causes TMAX=79 ºC, a second pulse produces values of from 92 to 96 ºC (the higher the temperature the shorter the INT). For 30 s pulses, TMAX=93 ºC for a single pulse, and varied from 98 to 104 ºC for a second pulse. CONCLUSIONS Applying a second RF pulse at the same ablation site increases lesion depth by 1 - 1.5 mm more than a single pulse and could lead to higher temperatures (up to 17 ºC). Both lesion depth and maximum tissue temperature increased at shorter inter-pulse intervals, which could cause clinical complications from overheating such as steam pops.
Collapse
Affiliation(s)
| | - Enrique Berjano
- BioMIT, Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| | - Ana González-Suárez
- Electrical and Electronic Engineering, National University of Ireland Galway, Ireland; Translational Medical Device Lab, National University of Ireland Galway, Ireland.
| |
Collapse
|
8
|
González-Suárez A, Pérez JJ, Irastorza RM, D'Avila A, Berjano E. Computer modeling of radiofrequency cardiac ablation: 30 years of bioengineering research. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2022; 214:106546. [PMID: 34844766 DOI: 10.1016/j.cmpb.2021.106546] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 11/08/2021] [Accepted: 11/15/2021] [Indexed: 06/13/2023]
Abstract
This review begins with a rationale of the importance of theoretical, mathematical and computational models for radiofrequency (RF) catheter ablation (RFCA). We then describe the historical context in which each model was developed, its contribution to the knowledge of the physics of RFCA and its implications for clinical practice. Next, we review the computer modeling studies intended to improve our knowledge of the biophysics of RFCA and those intended to explore new technologies. We describe the most important technical details of the implementation of mathematical models, including governing equations, tissue properties, boundary conditions, etc. We discuss the utility of lumped element models, which despite their simplicity are widely used by clinical researchers to provide a physical explanation of how RF power is absorbed in different tissues. Computer model verification and validation are also discussed in the context of RFCA. The article ends with a section on the current limitations, i.e. aspects not yet included in state-of-the-art RFCA computer modeling and on future work aimed at covering the current gaps.
Collapse
Affiliation(s)
- Ana González-Suárez
- Electrical and Electronic Engineering, National University of Ireland Galway, Ireland; Translational Medical Device Lab, National University of Ireland Galway, Ireland
| | - Juan J Pérez
- Department of Electronic Engineering, BioMIT, Universitat Politècnica de València, Valencia, Spain
| | - Ramiro M Irastorza
- Instituto de Física de Líquidos y Sistemas Biológicos (CONICET), La Plata, Argentina; Instituto de Ingeniería y Agronomía, Universidad Nacional Arturo Jauretche, Florencio Varela, Argentina
| | - Andre D'Avila
- Division of Cardiovascular Medicine, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States
| | - Enrique Berjano
- Department of Electronic Engineering, BioMIT, Universitat Politècnica de València, Valencia, Spain.
| |
Collapse
|
9
|
Rossmann C, Motamarry A, Panescu D, Haemmerich D. Computer simulations of an irrigated radiofrequency cardiac ablation catheter and experimental validation by infrared imaging. Int J Hyperthermia 2021; 38:1149-1163. [PMID: 34376106 DOI: 10.1080/02656736.2021.1961027] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
PURPOSE To develop and validate a three-dimensional (3-D) computer model based on accurate geometry of an irrigated cardiac radiofrequency (RF) ablation catheter with microwave radiometry capability, and to test catheter performance. METHODS A computer model was developed based on CAD geometry of a RF cardiac ablation catheter prototype to simulate electromagnetic heating, heat transfer, and computational fluid dynamics (blood flow, open irrigation, and natural convection). Parametric studies were performed; blood flow velocity (0-25 cm/s) and irrigation flow (0-40 ml/min) varied, both with perpendicular (PE) and parallel (PA) catheter orientations relative to tissue. Tissue Agar phantom studies were performed under similar conditions, and temperature maps were recorded via infrared camera. Computer model simulations were performed with constant voltage and with voltage adjusted to achieve maximum tissue temperatures of 95-105 °C. RESULTS Model predicted thermal lesion width at 5 W power was 5.8-6.4 mm (PE)/6.5-6.6 mm (PA), and lesion depth was 4.0-4.3 mm (PE)/4.0-4.1 mm (PA). Compared to phantom studies, the mean errors of the computer model were as follows: 6.2 °C(PE)/4.3 °C (PA) for maximum gel temperature, 0.7 mm (10.9%) (PE)/0.1 mm (0.8%) (PA) for lesion width, and 0.3 mm (7.7%)(PE)/0.7 mm (19.1%) (PA) for lesion depth. For temperature-controlled ablation, model predicted thermal lesion width was 7-9.2 mm (PE)/8.6-9.2 mm (PA), and lesion depth was 4.3-5.5 mm (PE)/3.4-5.4 mm (PA). CONCLUSIONS Computer models were able to reproduce device performance and to enable device evaluation under varying conditions. Temperature controlled ablation of irrigated catheters enables optimal tissue temperatures independent of patient-specific conditions such as blood flow.
Collapse
Affiliation(s)
- Christian Rossmann
- Department of Pediatrics, Medical University of South Carolina, Charleston, SC, USA.,AdditiveLab, Leuven, Belgium
| | - Anjan Motamarry
- Department of Pediatrics, Medical University of South Carolina, Charleston, SC, USA.,Department of Drug Discovery & Biomedical Sciences, Medical University of South Carolina, Charleston, SC, USA.,Wellman Center for Photomedicine, Massachusetts General Hospital/Harvard University, Boston, MA, USA
| | | | - Dieter Haemmerich
- Department of Pediatrics, Medical University of South Carolina, Charleston, SC, USA.,Department of Bioengineering, Clemson University, Clemson, SC, USA
| |
Collapse
|
10
|
Parés C, Berjano E, González-Suárez A. Effect of intracardiac blood flow pulsatility during radiofrequency cardiac ablation: computer modeling study. Int J Hyperthermia 2021; 38:316-325. [PMID: 33627008 DOI: 10.1080/02656736.2021.1890240] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
Abstract
PURPOSE To assess the effect of intracardiac blood flow pulsatility on tissue and blood distributions during radiofrequency (RF) cardiac ablation (RFCA). METHODS A three-dimensional computer model was used to simulate constant power ablations with an irrigated-tip electrode and three possible catheter orientations (perpendicular, parallel and 45°). Continuous flow and three different pulsatile flow profiles were considered, with four average blood velocity values: 3, 5.5, 8.5 and 24.4 cm/s. The 50 °C contour was used to assess thermal lesion size. RESULTS The differences in lesion size between continuous flow and the different pulsatile flow profiles were always less than 1 mm. As regards maximum tissue temperature, the differences between continuous and pulsatile flow were always less than 1 °C, with slightly higher differences in maximum blood temperature, but never over 6 °C. While the progress of maximum tissue temperature was identical for continuous and pulsatile flow, maximum blood temperature with the pulsatile profile showed small amplitude oscillations associated with blood flow pulsatility. CONCLUSIONS The findings show that intracardiac blood pulsatility has a negligible effect on lesion size and a very limited impact on maximum tissue and blood temperatures, which suggests that future experimental studies based on ex vivo or in silico models can ignore pulsatility in intracardiac blood flow.
Collapse
Affiliation(s)
| | - Enrique Berjano
- BioMIT, Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| | - Ana González-Suárez
- Electrical and Electronic Engineering, National University of Ireland Galway, Galway, Ireland.,Translational Medical Device Lab, National University of Ireland Galway, Galway, Ireland
| |
Collapse
|
11
|
Zhang M, Cheng Y, Liu H, Nan Q. Study on the effect of different blood flow velocities of pulmonary vein on endocardial microwave ablation of atrial fibrillation. Technol Health Care 2021; 30:29-41. [PMID: 33998563 DOI: 10.3233/thc-202421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
OBJECTIVE To cure atrial fibrillation, the maximum ablation depth (⩾ 50∘C) should exceed the myocardial thickness to achieve the effect of transmural ablation. The blood flow of pulmonary vein in the endocardium can cause the change in the myocardial temperature distribution. Therefore, the study investigated the effect of different pulmonary vein blood flow velocities on the endocardial microwave ablation. METHODS The finite element model of the endocardial microwave ablation of pulmonary vein was simulated by electromagnetic thermal flow coupling. The ablation power was 30 W and the ablation time was within 30 s. The blood flow in the coupling of fluid mechanics equation and heat transfer equation results in the heat damage. Furthermore, the cause of the different lesion dimensions is the blood flow velocity. The flow velocities were set as 0, 0.02, 0.05, 0.07, 0.12, 0.16, 0.20, 0.25 and 0.30 m/s. RESULTS When the flow velocities were 0, 0.02, 0.05, 0.07, 0.12, 0.16, 0.20, 0.25 and 0.30 m/s, the maximum ablation depth were 6.0, 5.56, 5.16, 5.12, 5.04, 5.01, 4.98, 4.96 and 4.94 mm, respectively; the maximum ablation width were 12.52, 9.63, 9.23, 9.16, 9.07, 9.05, 8.94, 8.91, 8.90 mm, respectively; the maximum ablation length were 12.00, 11.61, 8.98, 8.59, 8.37, 8.23, 8.16, 8.06 and 8.04 mm respectively. To achieve transmural ablation, the time was 3, 3, 3, 3, 3, 4, 4, 4, 4 s, respectively when the myocardial thickness was 2 mm; the time was 7, 8, 8, 8, 9, 9, 9, 9, 9 s, respectively when 3 mm; the time was 15, 16, 18, 19, 19, 20, 20, 20, 20 s, respectively when 4 mm. CONCLUSIONS When the velocity increases from 0 m/s to 3 m/s, the microwave lesion depth decreases by 1.06 mm. To achieve transmural ablation, when the myocardial thickness is 2 mm, 3 and 4 s should be taken when the velocity is 0-0.12 and 0.120.30 m/s, respectively; when the myocardial thickness is 3 mm, 7, 8 and 9 s should be taken when 0, 0-0.07 and 0.07-0.30 m/s respectively; when the myocardial thickness is 4 mm, 15, 16, 18, 19, 20 s should be taken when 0, 0-0.02, 0.02-0.05, 0.05-0.12, 0.12 m/s-0.30 m/s.
Collapse
|
12
|
Yan S, Gu K, Wu X, Wang W. Computer simulation study on the effect of electrode-tissue contact force on thermal lesion size in cardiac radiofrequency ablation. Int J Hyperthermia 2020; 37:37-48. [PMID: 31918588 DOI: 10.1080/02656736.2019.1708482] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
Purpose: In cardiac radiofrequency (RF) ablation, RF energy is often used to create a series of transmural lesions for blocking accessory conduction pathways. Electrode-tissue contact force (CF) is one of the key determinants of lesion formation during RF ablation. Low electrode-tissue CF is associated with ineffective RF lesion formation, whereas excessive CF may increase the risk of steam pop and perforation. By using finite element analysis, we studied lesion size and features at different values of electrode-tissue CF in cardiac RF ablation.Materials and methods: A computer-model-coupled electrode-tissue CF field, RF electric field, and thermal field were developed to study temperature distribution and lesion dimensions in cardiac tissue subjected to CF of 2, 5, 10, 20, 30, and 40 g with identical RF voltage and duration.Results: Increasing CF was associated with an increase in lesion depth, width, and cross-section area. The lesion cross-section area exhibited a linear increase, and the lesion width was significantly greater than lesion depth under the identical ablation condition. The relationship between CF value and lesion size is a power function: Lesion Size = a × CFb (Lesion Depth = 3.17 × CF0.14 and Lesion Width = 5.17 × CF0.14).Conclusions: This study confirmed that CF is a major determinant of RF lesion size and that electrode-tissue CF affects the amount of power dissipated in tissue. At a constant RF voltage and application time, RF lesion size increases as CF increases.
Collapse
Affiliation(s)
- Shengjie Yan
- Electronic Engineering Department, Fudan University, Shanghai, China
| | - Kaihao Gu
- Electronic Engineering Department, Fudan University, Shanghai, China
| | - Xiaomei Wu
- Electronic Engineering Department, Fudan University, Shanghai, China.,Key Laboratory of Medical Imaging Computing and Computer Assisted Intervention (MICCAI) of Shanghai, Fudan University, Shanghai, China.,Shanghai Engineering Research Center of Assistive Devices, Shanghai, China
| | - Weiqi Wang
- Electronic Engineering Department, Fudan University, Shanghai, China
| |
Collapse
|
13
|
Irastorza RM, Gonzalez-Suarez A, Pérez JJ, Berjano E. Differences in applied electrical power between full thorax models and limited-domain models for RF cardiac ablation. Int J Hyperthermia 2020; 37:677-687. [DOI: 10.1080/02656736.2020.1777330] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Affiliation(s)
- Ramiro M. Irastorza
- Instituto de Física de Líquidos y Sistemas Biológicos (CONICET), La Plata, Argentina
- Instituto de Ingeniería y Agronomía, Universidad Nacional Arturo Jauretche, Florencio Varela, Argentina
| | - Ana Gonzalez-Suarez
- Electrical and Electronic Engineering Department, National University of Ireland, Galway, Ireland
- Translational Medical Device Lab, National University of Ireland, Galway, Ireland
| | - Juan J. Pérez
- BioMIT, Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| | - Enrique Berjano
- BioMIT, Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| |
Collapse
|
14
|
Nguyen DM, Qian P, Barry T, McEwan A. The region-of-interest based measurement selection process for electrical impedance tomography in radiofrequency cardiac ablation with known anatomical information. Biomed Signal Process Control 2020. [DOI: 10.1016/j.bspc.2019.101706] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
|
15
|
Nguyen DM, Qian P, Barry T, McEwan A. Self-weighted NOSER-prior electrical impedance tomography using internal electrodes in cardiac radiofrequency ablation. Physiol Meas 2019; 40:065006. [DOI: 10.1088/1361-6579/ab1937] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
16
|
Dillon-Murphy D, Marlevi D, Ruijsink B, Qureshi A, Chubb H, Kerfoot E, O'Neill M, Nordsletten D, Aslanidi O, de Vecchi A. Modeling Left Atrial Flow, Energy, Blood Heating Distribution in Response to Catheter Ablation Therapy. Front Physiol 2019; 9:1757. [PMID: 30618785 PMCID: PMC6302108 DOI: 10.3389/fphys.2018.01757] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 11/20/2018] [Indexed: 11/16/2022] Open
Abstract
Introduction: Atrial fibrillation (AF) is a widespread cardiac arrhythmia that commonly affects the left atrium (LA), causing it to quiver instead of contracting effectively. This behavior is triggered by abnormal electrical impulses at a specific site in the atrial wall. Catheter ablation (CA) treatment consists of isolating this driver site by burning the surrounding tissue to restore sinus rhythm (SR). However, evidence suggests that CA can concur to the formation of blood clots by promoting coagulation near the heat source and in regions with low flow velocity and blood stagnation. Methods: A patient-specific modeling workflow was created and applied to simulate thermal-fluid dynamics in two patients pre- and post-CA. Each model was personalized based on pre- and post-CA imaging datasets. The wall motion and anatomy were derived from SSFP Cine MRI data, while the trans-valvular flow was based on Doppler ultrasound data. The temperature distribution in the blood was modeled using a modified Pennes bioheat equation implemented in a finite-element based Navier-Stokes solver. Blood particles were also classified based on their residence time in the LA using a particle-tracking algorithm. Results: SR simulations showed multiple short-lived vortices with an average blood velocity of 0.2-0.22 m/s. In contrast, AF patients presented a slower vortex and stagnant flow in the LA appendage, with the average blood velocity reduced to 0.08–0.14 m/s. Restoration of SR also increased the blood kinetic energy and the viscous dissipation due to the presence of multiple vortices. Particle tracking showed a dramatic decrease in the percentage of blood remaining in the LA for longer than one cycle after CA (65.9 vs. 43.3% in patient A and 62.2 vs. 54.8% in patient B). Maximum temperatures of 76° and 58°C were observed when CA was performed near the appendage and in a pulmonary vein, respectively. Conclusion: This computational study presents novel models to elucidate relations between catheter temperature, patient-specific atrial anatomy and blood velocity, and predict how they change from SR to AF. The models can quantify blood flow in critical regions, including residence times and temperature distribution for different catheter positions, providing a basis for quantifying stroke risks.
Collapse
Affiliation(s)
- Desmond Dillon-Murphy
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - David Marlevi
- School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Bram Ruijsink
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Ahmed Qureshi
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Henry Chubb
- Department of Cardiothoracic Surgery, Stanford University, Palo Alto, CA, United States
| | - Eric Kerfoot
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Mark O'Neill
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - David Nordsletten
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Oleg Aslanidi
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Adelaide de Vecchi
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| |
Collapse
|
17
|
González-Suárez A, Herranz D, Berjano E, Rubio-Guivernau JL, Margallo-Balbás E. Relation between denaturation time measured by optical coherence reflectometry and thermal lesion depth during radiofrequency cardiac ablation: Feasibility numerical study. Lasers Surg Med 2017; 50:222-229. [PMID: 29168554 DOI: 10.1002/lsm.22771] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/11/2017] [Indexed: 11/11/2022]
Abstract
BACKGROUND/OBJECTIVE Radiofrequency (RF) catheter ablation is a minimally invasive medical procedure used to thermally destroy the focus of cardiac arrhythmias. Novel optical techniques are now being integrated into RF catheters in order to detect the changes in tissue properties. Loss of birefringence due to fiber denaturation at around 70°C is related to changes in accumulated phase retardation and can be measured by polarization-sensitive optical coherence reflectometry (PS-OCR). Since irreversible thermal lesions are produced when the tissue reaches 50°C, our goal was to seek the mathematical relationship between both isotherms. MATERIALS AND METHODS A two-dimensional model based on a coupled electric-thermal problem was built and solved using the finite element method. The model consisted of cardiac tissue, blood, and a non-irrigated electrode with a sensor embedded in its tip to maintain a specific target electrode temperature. Computer simulations were conducted by varying the tissue characteristics. Lesion depth was estimated by the 50°C isotherm, while the denaturation time (TD) was taken as the time at which the 70°C isotherm reached a depth of 0.75 mm (which corresponds to the optical depth reached by PS-OCR technology). RESULTS A strong correlation (R2 > 0.83) was found between TD and lesion depth and an even stronger correlation (R2 > 0.96) was found between TD and the time required to achieve a specific lesion depth. For instance, the ablation time required to ensure a minimum lesion depth of 3 mm was 1.33 × TD + 3.93 × seconds. CONCLUSIONS The computer results confirmed the strong relationship between denaturation time and lesion depth and suggest that measuring denaturation time by PS-OCR could provide information on the ablation time required to reach a specific lesion depth. Lasers Surg. Med. 50:222-229, 2018. © 2017 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Ana González-Suárez
- Department of Information and Communication Technologies, Universitat Pompeu Fabra, Barcelona, Spain
| | | | - Enrique Berjano
- BioMIT, Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| | | | | |
Collapse
|
18
|
Pérez JJ, González-Suárez A, Berjano E. Numerical analysis of thermal impact of intramyocardial capillary blood flow during radiofrequency cardiac ablation. Int J Hyperthermia 2017; 34:243-249. [DOI: 10.1080/02656736.2017.1336258] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Affiliation(s)
- Juan J. Pérez
- BioMIT-Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| | - Ana González-Suárez
- BioMIT-Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| | - Enrique Berjano
- BioMIT-Department of Electronic Engineering, Universitat Politècnica de València, Valencia, Spain
| |
Collapse
|
19
|
Yan S, Wu X, Wang W. Theoretical and experimental analysis of amplitude control ablation and bipolar ablation in creating linear lesion and discrete lesions for treating atrial fibrillation. Int J Hyperthermia 2017; 33:608-616. [DOI: 10.1080/02656736.2017.1286390] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Affiliation(s)
- Shengjie Yan
- Electronic Engineering Department, Fudan University, Shanghai, China
| | - Xiaomei Wu
- Electronic Engineering Department, Fudan University, Shanghai, China
- Shanghai Engineering Research Center of Assistive Devices, Shanghai, China
- Key Laboratory of Medical Imaging Computing and Computer Assisted Intervention (MICCAI) of Shanghai, Fudan University, Shanghai, China
| | - Weiqi Wang
- Electronic Engineering Department, Fudan University, Shanghai, China
| |
Collapse
|
20
|
Yan S, Wu X, Wang W. A simulation study to compare the phase-shift angle radiofrequency ablation mode with bipolar and unipolar modes in creating linear lesions for atrial fibrillation ablation. Int J Hyperthermia 2016; 32:231-8. [DOI: 10.3109/02656736.2016.1145746] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
|
21
|
Gonzalez-Suarez A, Berjano E. Comparative Analysis of Different Methods of Modeling the Thermal Effect of Circulating Blood Flow During RF Cardiac Ablation. IEEE Trans Biomed Eng 2016; 63:250-9. [DOI: 10.1109/tbme.2015.2451178] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
22
|
Zhang M, Zhou Z, Wu S, Lin L, Gao H, Feng Y. Simulation of temperature field for temperature-controlled radio frequency ablation using a hyperbolic bioheat equation and temperature-varied voltage calibration: a liver-mimicking phantom study. Phys Med Biol 2015; 60:9455-71. [DOI: 10.1088/0031-9155/60/24/9455] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
23
|
Milan HF, Carvalho CA, Maia AS, Gebremedhin KG. Graded meshes in bio-thermal problems with transmission-line modeling method. J Therm Biol 2014; 45:43-53. [DOI: 10.1016/j.jtherbio.2014.07.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 07/07/2014] [Accepted: 07/08/2014] [Indexed: 10/25/2022]
|
24
|
Manuchehrabadi N, Zhu L. Development of a computational simulation tool to design a protocol for treating prostate tumours using transurethral laser photothermal therapy. Int J Hyperthermia 2014; 30:349-61. [PMID: 25244058 DOI: 10.3109/02656736.2014.948497] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES The objective of this study was to design laser treatment protocols to induce sufficient thermal damage to a tumour embedded in a prostate model, while protecting the surrounding healthy tissue. METHODS A computational Monte Carlo simulation algorithm of light transport in a spherical prostatic tumour containing gold nanorods was developed to determine laser energy deposition. The laser energy absorption was then used to simulate temperature elevations in the tumour embedded in an elliptical human prostate model. The Arrhenius integral was coupled with the heat transfer model to identify heating protocols to induce 100% damage to the tumour, while resulting in less than 5% damage to the surrounding sensitive prostatic tissue. RESULTS Heating time to achieve 100% damage to the tumour was identified to be approximately 630 s when using a laser irradiance of 7 W/cm2 incident on the prostatic urethral surface. Parametric studies were conducted to show how the local blood perfusion rate and urethral surface cooling affect the heating time to achieve the same thermal dosage. The heating time was shorter when cooling at the urethra was not applied and/or with heat-induced vasculature damage. The identified treatment protocols were acceptable since the calculated percentages of the damaged healthy tissue volume to the healthy prostatic volume were approximately 2%, less than the threshold of 5%. The approach and results from this study can be used to design individualised treatment protocols for patients suffering from prostatic cancer.
Collapse
Affiliation(s)
- Navid Manuchehrabadi
- Department of Mechanical Engineering, University of Maryland Baltimore County , Baltimore, Maryland , USA
| | | |
Collapse
|
25
|
Gallagher N, Fear EC, Byrd IA, Vigmond EJ. Contact geometry affects lesion formation in radio-frequency cardiac catheter ablation. PLoS One 2013; 8:e73242. [PMID: 24086275 PMCID: PMC3781109 DOI: 10.1371/journal.pone.0073242] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2013] [Accepted: 07/18/2013] [Indexed: 11/19/2022] Open
Abstract
One factor which may be important for determining proper lesion creation during atrial ablation is catheter-endocardial contact. Little information is available that relates geometric contact, depth and angle, to ablation lesion formation. We present an electrothermal computer model of ablation that calculated lesion volume and temperature development over time. The Pennes bioheat equation was coupled to a quasistatic electrical problem to investigate the effect of catheter penetration depth, as well as incident catheter angle as may occur in practice. Biological experiments were performed to verify the modelling of electrical phenomena. Results show that for deeply penetrating tips, acute catheter angles reduced the rate of temperature buildup, allowing larger lesions to form before temperatures elevated excessively. It was also found that greater penetration did not lead to greater transmurality of lesions. We conclude that catheter contact angle plays a significant role in lesion formation, and the time course must be considered. This is clinically relevant because proper identification and prediction of geometric contact variables could improve ablation efficacy.
Collapse
Affiliation(s)
- Neal Gallagher
- Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta, Canada
| | - Elise C. Fear
- Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta, Canada
| | - Israel A. Byrd
- St. Jude Medical, Atrial Fibrillation Technology Development, St. Paul, Minnesota, United States of America
| | - Edward J. Vigmond
- Department of Electrical and Computer Engineering, University of Calgary, Calgary, Alberta, Canada
- LIRYC Electrophysiology and Heart Modeling Institute/Laboratoire Institut de Modélisation, Université Bordeaux 1, Pessac, France
| |
Collapse
|
26
|
Gallagher NP, Fear EC, Vigmond EJ, Byrd IA. Cathether contact geometry affects lesion formation in radio-frequency cardiac catheter ablation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:243-6. [PMID: 22254295 DOI: 10.1109/iembs.2011.6090046] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
One factor which may be important for determining proper lesion creation in an atrial ablation procedure is catheter-endocardial contact. Little information is available that relates geometric contact, depth and angle, to ablation lesion formation. We present an electrothermal computer model of ablation that calculates lesion volume and temperature development over time. The Pennes bioheat equation was coupled to a quasistatic electrical problem. This method simulates importantly, not just catheter penetration depth, but also several different incident catheter angles as may occur in practise. Results show that for deeply penetrating tips, greater catheter angles reduce the rate of temperature buildup, allowing for larger lesions to form before temperatures become dangerous. It was also found that greater penetration may not lead to greater transmurality in lesion formation. We conclude that catheter contact angle plays a significant role in lesion formation, and the time course must be considered. This is clinically relevant because it makes proper identification and prediction of geometric contact variables a necessity in order to improve ablation efficacy and safety.
Collapse
Affiliation(s)
- Neal P Gallagher
- Department of Electrical and Computer Engineering, University of Calgary, Calgary, AB, Canada T2N 1N4.
| | | | | | | |
Collapse
|
27
|
Watanabe H, Yamazaki N, Kobayashi Y, Miyashita T, Ohdaira T, Hashizume M, Fujie MG. Estimation of intraoperative blood flow during liver RF ablation using a finite element method-based biomechanical simulation. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:7441-5. [PMID: 22256059 DOI: 10.1109/iembs.2011.6091745] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Radiofrequency ablation is increasingly being used for liver cancer because it is a minimally invasive treatment method. However, it is difficult for the operators to precisely control the formation of coagulation zones because of the cooling effect of capillary vessels. To overcome this limitation, we have proposed a model-based robotic ablation system using a real-time numerical simulation to analyze temperature distributions in the target organ. This robot can determine the adequate amount of electric power supplied to the organ based on real-time temperature information reflecting the cooling effect provided by the simulator. The objective of this study was to develop a method to estimate the intraoperative rate of blood flow in the target organ to determine temperature distribution. In this paper, we propose a simulation-based method to estimate the rate of blood flow. We also performed an in vitro study to validate the proposed method by estimating the rate of blood flow in a hog liver. The experimental results revealed that the proposed method can be used to estimate the rate of blood flow in an organ.
Collapse
Affiliation(s)
- Hiroki Watanabe
- Graduate School of Science and Engineering, Waseda University, Japan.
| | | | | | | | | | | | | |
Collapse
|
28
|
Alba-Martínez J, Trujillo M, Blasco-Giménez R, Berjano E. Could it be advantageous to tune the temperature controller during radiofrequency ablation? A feasibility study using theoretical models. Int J Hyperthermia 2011; 27:539-48. [DOI: 10.3109/02656736.2011.586665] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
|
29
|
Abstract
Background:
The estimation of lesion size is an integral part of treatment planning for the clinical applications of radiofrequency ablation. However, to date, studies have not directly evaluated the impact of different computational estimation techniques for predicting lesion size. In this study, we focus on three common methods used for predicting tissue injury: (1) iso-temperature contours, (2) Cumulative equivalent minutes, (3) Arrhenius based thermal injury.
Methods:
We created a geometric model of a multi-tyne ablation electrode and simulated thermal and tissue injury profiles that result from three calculation methods after 15 minutes exposure to a constant RF voltage source. A hybrid finite element technique was used to calculate temperature and tissue injury. Time-temperature curves were used in the assessment of iso-temperature thresholds and the method of cumulative equivalent minutes. An Arrhenius-based formulation was used to calculate sequential and recursive thermal injury to tissues.
Results:
The data demonstrate that while iso-temperature and cumulative equivalent minute contours are similar in shape, these two methodologies grossly over-estimate the amount of tissue injury when compared to recursive thermal injury calculations, which have previously been shown to correlate closely with in vitro pathologic lesion volume measurement. In addition, Arrhenius calculations that do not use a recursive algorithm result in a significant underestimation of lesion volume. The data also demonstrate that lesion width and depth are inadequate means of characterizing treatment volume for multi-tine ablation devices.
Conclusions:
Recursive thermal injury remains the most physiologically relevant means of computationally estimating lesion size for hepatic tumor applications. Iso-thermal and cumulative equivalent minute approaches may produce significant errors in the estimation of lesion size.
Collapse
|
30
|
Chang IA. Considerations for thermal injury analysis for RF ablation devices. Open Biomed Eng J 2010; 4:3-12. [PMID: 20300227 PMCID: PMC2840607 DOI: 10.2174/1874120701004020003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2009] [Revised: 11/15/2009] [Accepted: 12/19/2009] [Indexed: 12/18/2022] Open
Abstract
BACKGROUND The estimation of lesion size is an integral part of treatment planning for the clinical applications of radiofrequency ablation. However, to date, studies have not directly evaluated the impact of different computational estimation techniques for predicting lesion size. In this study, we focus on three common methods used for predicting tissue injury: (1) iso-temperature contours, (2) Cumulative equivalent minutes, (3) Arrhenius based thermal injury. METHODS We created a geometric model of a multi-tyne ablation electrode and simulated thermal and tissue injury profiles that result from three calculation methods after 15 minutes exposure to a constant RF voltage source. A hybrid finite element technique was used to calculate temperature and tissue injury. Time-temperature curves were used in the assessment of iso-temperature thresholds and the method of cumulative equivalent minutes. An Arrhenius-based formulation was used to calculate sequential and recursive thermal injury to tissues. RESULTS The data demonstrate that while iso-temperature and cumulative equivalent minute contours are similar in shape, these two methodologies grossly over-estimate the amount of tissue injury when compared to recursive thermal injury calculations, which have previously been shown to correlate closely with in vitro pathologic lesion volume measurement. In addition, Arrhenius calculations that do not use a recursive algorithm result in a significant underestimation of lesion volume. The data also demonstrate that lesion width and depth are inadequate means of characterizing treatment volume for multi-tine ablation devices. CONCLUSIONS Recursive thermal injury remains the most physiologically relevant means of computationally estimating lesion size for hepatic tumor applications. Iso-thermal and cumulative equivalent minute approaches may produce significant errors in the estimation of lesion size.
Collapse
Affiliation(s)
- Isaac A Chang
- U.S. Food and Drug Administration, White Oak, MD 20993, USA
| |
Collapse
|
31
|
Schutt D, Berjano EJ, Haemmerich D. Effect of electrode thermal conductivity in cardiac radiofrequency catheter ablation: a computational modeling study. Int J Hyperthermia 2009; 25:99-107. [PMID: 19337910 DOI: 10.1080/02656730802563051] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022] Open
Abstract
PURPOSE Radiofrequency (RF ablation) is the treatment of choice for certain types of cardiac arrhythmias. Recent studies have suggested that using gold instead of platinum as the electrode material for cardiac catheter ablation leads to larger thermal lesions due to its higher thermal conductivity. In this study we created computer models to compare the effects of different electrode materials on lesion dimensions using different catheters, insertion depths, and flow rates. MATERIALS AND METHODS Finite element method (FEM) models of two cardiac ablation electrodes (7Fr, length 4 mm and 8Fr, length 10 mm) made of platinum, gold, and copper were created with tissue insertion depths of 0.75, 1.25, and 2.5 mm. Convective cooling was applied to the electrode and tissue based on measurements from previous studies at different flow rates. RF ablations were simulated with both temperature control and constant power control algorithms to determine temperature profiles after 60 s. RESULTS With the constant power algorithm there was no difference in lesion dimensions between the electrode materials over the range of parameters. With the temperature control algorithm, lesion width and depth were only marginally larger ( approximately 0.1-0.7 mm) with the gold and copper electrodes compared to the platinum electrode for all parameter combinations. CONCLUSION Our computer modelling results show only minor increases in thermal lesion dimensions with electrode materials of higher thermal conductivity. These observed differences likely do not provide a significant advantage during clinical procedures.
Collapse
Affiliation(s)
- David Schutt
- Medical University of South Carolina, Charleston, South Carolina, Charleston, SC 29425, USA
| | | | | |
Collapse
|
32
|
Pichardo S, Hynynen K. New design for an endoesophageal sector- based array for the treatment of atrial fibrillation: a parametric simulation study. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2009; 56:600-612. [PMID: 19411218 DOI: 10.1109/tuffc.2009.1076] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Atrial fibrillation (AF) is the most frequent and sustained cardiac arrhythmia affecting humans. The electrical isolation by ablation of the pulmonary veins (PV) in the left atrium (LA) of the heart has proved to be an effective cure for the AF. The ablation consists mainly of the formation of a localized circumferential thermal coagulation of the cardiac tissue surrounding the PVs. In this article, a parametric study was carried out to establish an optimal configuration of endesophageal ultrasound phased arrays intended to treat the AF. The devices are spherical-surface sections truncated at 15 mm, with a depth of 4 mm, and they are cut in concentric-rings, each composed of independently driven sectors. The number of independent elements (N(e)) was minimized for different values of ratio of pressure amplitude of the secondary lobe over the main lobe (eta) of 0.35, 0.4, 0.45, and 0.5 inside a volume of interest (VOI). After assuming a Cartesian system with the origin in the center of the device, the VOI was defined as the prism enclosed by the coordinates (-12, 10, -9) mm and (12, 37, 9) mm. The VOI has its center at (0, 23.5, 0) mm and is large enough to contain all the targets identified in the Visible Human Project Male specimen. Operating at 1 MHz, eta and N(e)were calculated in function of the element size and focal length (F). Four devices for each value of eta were found. After keeping values of F and normalized dimensions of the independent elements in terms of wavelength, higher frequencies were considered: 1.25 MHz, 1.5 MHz, and 2 MHz. In total, 16 device configurations were obtained. Realistic modeling of lesion formation in the heart chamber showed that the 16 configurations were able to produce the typical lesion used to treat the AF while preserving surrounding structures. At higher frequencies, lower power was required, and a greater number of array elements was required. For an exposure of 5 s and a maximum temperature of 70 degrees C, the average (+/-s.d.) acoustical intensity at transducer surface varied from 22.3(+/-5.8) W/cm(2) for a device with F = 98 mm at 1 MHz to 5.8(+/-1.2) W/cm(2) for a device with F = 186 mm at 2 MHz, while requiring 319 and 2093 elements, respectively, and achieving values of eta of 0.5 and 0.41, respectively. For the intended application, the selected devices implied a better focusing when compared with more traditional planar 2-D arrays, while requiring less power and fewer independent elements.
Collapse
Affiliation(s)
- Samuel Pichardo
- Thunder Bay Regional Research Institute, Thunder Bay, Canada.
| | | |
Collapse
|
33
|
Pilcher TA, Saul JP, Hlavacek AM, Haemmerich D. Contrasting effects of convective flow on catheter ablation lesion size: cryo versus radiofrequency energy. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2008; 31:300-7. [PMID: 18307624 DOI: 10.1111/j.1540-8159.2008.00989.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Cryoablation has now become an alternative to treat many cardiac arrhythmias, and may be the treatment of choice in some patient populations. We compared the effects of convective flow on large-tip cryo and radiofrequency (RF) lesions dimensions. METHODS Cryoablation and RF ablation were performed on porcine heart sections in a saline bath with varying directed flow rates. Cryoablation was performed for 4 minutes on 50 tissue pieces with tip temperature controlled at -80 degrees C. RF ablation was performed on 50 tissue pieces for 60 seconds at 60 degrees C tip temperature. The pieces were placed in culture media for 24 hours, and then sectioned, stained, and measured. RESULTS Cryoablation and RF lesion sizes varied significantly with flow such that higher flow rates produced smaller cryoablation lesions and larger RF lesions (mean cryoablation volumes: 854 +/- 402, 808 +/- 217, 781 +/- 217, 359 +/- 114, and 292 +/- 117 mm(3), and mean RF volumes: 211 +/- 35, 304 +/- 79, 439 +/- 125, 525 +/- 187, and 597 +/- 126 mm(3) for 0, 1, 2, 3, and 5 L/min flow rates, respectively, P < 0.0005). Trabeculated pieces had larger cryoablation lesions and smaller RF lesions than nontrabeculated ones at higher flow rate (P < 0.005). Cryoablation lesion volume increased as the time to reach -80 degrees C decreased (r(2)= 0.72). CONCLUSION In contrast to RF ablation, cryoablation lesion size is smaller at high flow rates, and larger at low flow rates due to the warming effects of local convective flow. The effects of high flow are reduced in areas of trabeculation, and the time to reach -80 degrees C predicts cryoablation lesion size.
Collapse
Affiliation(s)
- Thomas A Pilcher
- Division of Pediatric Cardiology, Medical University of South Carolina, Charleston, South Carolina 29425, USA
| | | | | | | |
Collapse
|
34
|
Haemmerich D, Pilcher TA. Convective cooling affects cardiac catheter cryoablation and radiofrequency ablation in opposite directions. ACTA ACUST UNITED AC 2008; 2007:1499-502. [PMID: 18002251 DOI: 10.1109/iembs.2007.4352585] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Recently, cryoablation has received increased attention as a safer alternative to radiofrequency (RF) ablation. The purpose of this study was to compare the effect of convective cooling at physiologic flow rates on RF lesion size and on cryo lesion size. Porcine hearts were sectioned into 40 pieces and placed in a temperature-controlled saline bath (37 degrees C) with varying directed flow rates (0, 1, 2 and 3 L/min). Large-tip cryoablation (8 mm tip) was performed for 4 minutes on 20 tissue sections at -80 degrees C tip temperature. Large-tip RF catheter ablation (10 mm tip) was performed at 60 degrees C target temperature for 1 minute on 20 tissue sections. For each catheter, flow rates were randomized between applications. The tissue pieces were placed in culture medium for 24 hrs, sectioned, stained and measured to determine lesion depth, width and volume. Average lesion geometry was estimated from the data. Lesion dimensions were dependent on the flow rate for RF ablation with larger lesions at higher flow rates (mean volumes: 211+/-35, 304+/-79, 439+/-125 and 525.7+/-187 mm3 for 0, 1, 2 and 3 L/min flow rate, respectively, p<0.01). Also for cryoablation lesion size varied significantly with flow, such that lower flow rates produced larger lesions (mean volumes: 855+/-402, 809+/-218, 658+/-91 and 360+/-14 mm3 for 0, 1, 2 and 3 L/min flow rate respectively, p<0.01). While RF ablation creates larger lesions at high flow rates (3 L/min), cryoablation creates larger lesions at low flow rates (0-1 L/min, p<0.05).
Collapse
Affiliation(s)
- Dieter Haemmerich
- Medical University of South Carolina, Division of Pediatric Cardiology, Charleston, SC 29414, USA.
| | | |
Collapse
|
35
|
Lequerica JL, Berjano EJ, Herrero M, Melecio L, Hornero F. A cooled water-irrigated intraesophageal balloon to prevent thermal injury during cardiac ablation: experimental study based on an agar phantom. Phys Med Biol 2008; 53:N25-34. [DOI: 10.1088/0031-9155/53/4/n01] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
|
36
|
Haemmerich D, Saul JP. Quantification of local convectional cooling during cardiac radiofrequency catheter ablation. CONFERENCE PROCEEDINGS : ... ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL CONFERENCE 2007; 2006:6293-6. [PMID: 17945951 DOI: 10.1109/iembs.2006.259993] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Radiofrequency (RF) catheter ablation is an effective, minimally invasive treatment method in clinical use for treatment of different cardiac arrhythmia. Studies have shown that lesion dimensions strongly depend on blood flow mediated convective cooling at the ablation site. We present a simple method to quantify convective cooling. A brief pulse of RF energy (10 W for 5 s) is applied, and catheter tip temperature is measured during and after energy application. Two parameters are extracted: 1) maximum tip temperature increase, and 2) slope of temperature decay 8 degree C above initial temperature. We tested whether these parameters can quantify convective cooling in ex vivo experiments. A RF catheter was inserted into a tissue phantom placed in a saline bath. Flow at different rates of 0, 1, 2 and 3 L/min was injected towards the catheter, and the parameters were extracted. Both parameters correlated with flow rate. Slope of temperature decay showed linear dependence on flow rate, maximum temperature increase showed exponential dependence. The parameters are potentially useful in quantifying convective cooling before ablation to predict lesion dimensions.
Collapse
Affiliation(s)
- D Haemmerich
- Div. of Pediatric Cardiology, Med. Univ. of South Carolina, Charleston, SC, USA
| | | |
Collapse
|
37
|
Pichardo S, Hynynen K. Circumferential lesion formation around the pulmonary veins in the left atrium with focused ultrasound using a 2D-array endoesophageal device: a numerical study. Phys Med Biol 2007; 52:4923-42. [PMID: 17671344 DOI: 10.1088/0031-9155/52/16/014] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Atrial fibrillation (AF) is the most frequently sustained cardiac arrhythmia affecting humans. The electrical isolation by ablation of the pulmonary veins (PVs) in the left atrium (LA) of the heart has been proven as an effective cure of AF. The ablation consists mainly in the formation of a localized circumferential thermal coagulation of the cardiac tissue surrounding the PVs. In the present numerical study, the feasibility of producing the required circumferential lesion with an endoesophageal ultrasound probe is investigated. The probe operates at 1 MHz and consists of a 2D array with enough elements (114 x 20) to steer the acoustic field electronically in a volume comparable to the LA. Realistic anatomical conditions of the thorax were considered from the segmentation of histological images of the thorax. The cardiac muscle and the blood-filled cavities in the heart were identified and considered in the sound propagation and thermal models. The influence of different conditions of the thermal sinking in the LA chamber was also studied. The circumferential ablation of the PVs was achieved by the sum of individual lesions induced with the proposed device. Different scenarios of lesion formation were considered where ultrasound exposures (1, 2, 5 and 10 s) were combined with maximal peak temperatures (60, 70 and 80 degrees C). The results of this numerical study allowed identifying the limits and best conditions for controlled lesion formation in the LA using the proposed device. A controlled situation for the lesion formation surrounding the PVs was obtained when the targets were located within a distance from the device in the range of 26 +/- 7 mm. When combined with a maximal temperature of 70 degrees C and an exposure time between 5 and 10 s, this distance ensured preservation of the esophageal structures, controlled lesion formation and delivery of an acoustic intensity at the transducer surface that is compatible with existing materials. With a peak temperature of 70 degrees C, the device and setup presented here induced highly localized lesions with a lesion volume varying from 10 +/- 4 to 18 +/- 7 mm(3) for an ultrasound exposure between 5 and 10 s, respectively, while the intensity varied from 26 +/- 7 to 20 +/- 6 W cm(-2).
Collapse
Affiliation(s)
- Samuel Pichardo
- Imaging Research-Sunnybrook Health Sciences Centre, 2075 Bayview Avenue, Room C713, Toronto, Ontario, Canada.
| | | |
Collapse
|
38
|
Pilcher TA, Sanford AL, Saul JP, Haemmerich D. Convective cooling effect on cooled-tip catheter compared to large-tip catheter radiofrequency ablation. PACING AND CLINICAL ELECTROPHYSIOLOGY: PACE 2007; 29:1368-74. [PMID: 17201844 DOI: 10.1111/j.1540-8159.2006.00549.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Both actively cooled-tip and large-tip catheters are currently available clinically to create large endomyocardial lesions during application of radiofrequency (RF) energy. The purpose of this study was to compare the effect of convective cooling at physiologic flow rates on RF lesion size using both actively cooled and large-tip catheters. METHODS Porcine hearts were sectioned into 72 pieces and placed in a temperature-controlled saline bath (37 degrees C) with varying directed flow rates (0, 1, 2, and 3 L/min). Cooled-tip RF ablation (4 mm tip) was performed for 1 minute on 36 tissue sections with power manually titrated to keep tip temperature below 40 degrees C. Large-tip catheter ablation (10 mm tip) was performed at 65 degrees C target temperature for 1 minute on 36 tissue sections. For each catheter, flow rates were randomized between applications. The tissue pieces were sectioned and measured to determine lesion depth, width, and volume. RESULTS Lesion dimensions were independent of the flow rate for the cooled-tip catheter (mean volumes: 382.0 +/- 121.6, 419.9 +/- 133.4, 375.9 +/- 169.1, and 346.7 +/- 173.4 mm(3) for 0, 1, 2, and 3 L/min flow rate, respectively, P = 0.78). For the large-tip catheter, lesion size varied significantly with flow, such that higher flow rates produced larger lesions (mean volumes: 120.7 +/- 50.7, 256.5 +/- 97.9, 393.4 +/- 149.9, and 548.9 +/- 157.0 mm(3) for 0, 1, 2, and 3 L/min flow rate respectively, P < 0.001) CONCLUSION During RF ablation, blood flow rate significantly affects lesion size for large-tip but not cooled-tip catheters. At low flow rates (0-1 L/min) cooled-tip catheters create larger lesions, while at high flow rates (3 L/min) large-tip catheters create larger lesions.
Collapse
Affiliation(s)
- Thomas A Pilcher
- Division of Pediatric Cardiology, Medical University of South Carolina, Charleston, South Carolina 29425, USA
| | | | | | | |
Collapse
|
39
|
Tangwongsan C, Chachati L, Webster JG, Farrell PV. In vitro calibration of a system for measurement of in vivo convective heat transfer coefficient in animals. Biomed Eng Online 2006; 5:57. [PMID: 17067386 PMCID: PMC1635717 DOI: 10.1186/1475-925x-5-57] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Accepted: 10/26/2006] [Indexed: 11/24/2022] Open
Abstract
Background We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver. Methods We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a Wheatstone-bridge circuit, similar to a hot-wire anemometer circuit. One arm is connected to a steerable catheter sensor whose tip is a 1.9 mm × 3.2 mm thin film resistive temperature detector (RTD) sensor. We used a circulation system to simulate different flow rates at 39°C for in vitro experiments using distilled water, tap water and saline. We heated the sensor approximately 5°C above the fluid temperature. We measured the power consumed by the sensor and the resistance of the sensor during the experiments and analyzed these data to determine the value of the convective heat transfer coefficient at various flow rates. Results From 0 to 5 L/min, experimental values of h in W/(m2·K) were for distilled water 5100 to 13000, for tap water 5500 to 12300, and for saline 5400 to 13600. Theoretical values were 1900 to 10700. Conclusion We believe this system is the smallest, most accurate method of minimally invasive measurement of in vivo h in animals and provides the least disturbance of flow.
Collapse
Affiliation(s)
- Chanchana Tangwongsan
- Department of Electrical Engineering, Chulalongkorn University Phaya-Thai Road, Bangkok 10330, Thailand.
| | | | | | | |
Collapse
|
40
|
Berjano EJ. Theoretical modeling for radiofrequency ablation: state-of-the-art and challenges for the future. Biomed Eng Online 2006; 5:24. [PMID: 16620380 PMCID: PMC1459161 DOI: 10.1186/1475-925x-5-24] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2006] [Accepted: 04/18/2006] [Indexed: 01/09/2023] Open
Abstract
Radiofrequency ablation is an interventional technique that in recent years has come to be employed in very different medical fields, such as the elimination of cardiac arrhythmias or the destruction of tumors in different locations. In order to investigate and develop new techniques, and also to improve those currently employed, theoretical models and computer simulations are a powerful tool since they provide vital information on the electrical and thermal behavior of ablation rapidly and at low cost. In the future they could even help to plan individual treatment for each patient. This review analyzes the state-of-the-art in theoretical modeling as applied to the study of radiofrequency ablation techniques. Firstly, it describes the most important issues involved in this methodology, including the experimental validation. Secondly, it points out the present limitations, especially those related to the lack of an accurate characterization of the biological tissues. After analyzing the current and future benefits of this technique it finally suggests future lines and trends in the research of this area.
Collapse
Affiliation(s)
- Enrique J Berjano
- Center for Research and Innovation on Bioengineering, Valencia Polytechnic University, Camino de Vera s/n, 46022 Valencia, Spain.
| |
Collapse
|
41
|
Mackerle J. Finite element modelling and simulations in cardiovascular mechanics and cardiology: A bibliography 1993–2004. Comput Methods Biomech Biomed Engin 2005; 8:59-81. [PMID: 16154871 DOI: 10.1080/10255840500141486] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
The paper gives a bibliographical review of the finite element modelling and simulations in cardiovascular mechanics and cardiology from the theoretical as well as practical points of views. The bibliography lists references to papers, conference proceedings and theses/dissertations that were published between 1993 and 2004. At the end of this paper, more than 890 references are given dealing with subjects as: Cardiovascular soft tissue modelling; material properties; mechanisms of cardiovascular components; blood flow; artificial components; cardiac diseases examination; surgery; and other topics.
Collapse
Affiliation(s)
- Jaroslav Mackerle
- Department of Mechanical Engineering, Linköping Institute of Technology, Sweden.
| |
Collapse
|
42
|
Fahey BJ, Nightingale KR, McAleavey SA, Palmeri ML, Wolf PD, Trahey GE. Acoustic radiation force impulse imaging of myocardial radiofrequency ablation: initial in vivo results. IEEE TRANSACTIONS ON ULTRASONICS, FERROELECTRICS, AND FREQUENCY CONTROL 2005; 52:631-41. [PMID: 16060512 DOI: 10.1109/tuffc.2005.1428046] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Acoustic radiation force impulse (ARFI) imaging techniques were used to monitor radiofrequency (RF) ablation of ovine cardiac tissue in vivo. Additionally, ARFI M-mode imaging methods were used to interrogate both healthy and ablated regions of myocardial tissue. Although induced cardiac lesions were not visualized well in conventional B-mode images, ARFI images of ablation procedures allowed determination of lesion location, shape, and relative size through time. The ARFI M-mode images were capable of distinguishing differences in behavior through the cardiac cycle between healthy and damaged tissue regions. As conventional sonography is often used to guide ablation catheters, ARFI imaging, which requires no additional equipment, may be a convenient modality for monitoring lesion formation in vivo.
Collapse
Affiliation(s)
- Brian J Fahey
- Department of Biomedical Engineering, Duke University, Durham, NC, USA.
| | | | | | | | | | | |
Collapse
|
43
|
Lai YC, Choy YB, Haemmerich D, Vorperian VR, Webster JG. Lesion size estimator of cardiac radiofrequency ablation at different common locations with different tip temperatures. IEEE Trans Biomed Eng 2004; 51:1859-64. [PMID: 15490835 DOI: 10.1109/tbme.2004.831529] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Finite element method (FEM) analysis has become a common method to analyze the lesion formation during temperature-controlled radiofrequency (RF) cardiac ablation. We present a process of FEM modeling a system including blood, myocardium, and an ablation catheter with a thermistor embedded at the tip. The simulation used a simple proportional-integral (PI) controller to control the entire process operated in temperature-controlled mode. Several factors affect the lesion size such as target temperature, blood flow rate, and application time. We simulated the time response of RF ablation at different locations by using different target temperatures. The applied sites were divided into two groups each with a different convective heat transfer coefficient. The first group was high-flow such as the atrioventricular (AV) node and the atrial aspect of the AV annulus, and the other was low-flow such as beneath the valve or inside the coronary sinus. Results showed the change of lesion depth and lesion width with time, under different conditions. We collected data for all conditions and used it to create a database. We implemented a user-interface, the lesion size estimator, where the user enters set temperature and location. Based on the database, the software estimated lesion dimensions during different applied durations. This software could be used as a first-step predictor to help the electrophysiologist choose treatment parameters.
Collapse
Affiliation(s)
- Yu-Chi Lai
- Department of Electrical and Computer Engineering, University of Wisconsin, Madison, WI 53706, USA
| | | | | | | | | |
Collapse
|
44
|
Tangwongsan C, Will JA, Webster JG, Meredith KL, Mahvi DM. In Vivo Measurement of Swine Endocardial Convective Heat Transfer Coefficient. IEEE Trans Biomed Eng 2004; 51:1478-86. [PMID: 15311835 DOI: 10.1109/tbme.2004.828035] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We measured the endocardial convective heat transfer coefficient h at 22 locations in the cardiac chambers of 15 pigs in vivo. A thin-film Pt catheter tip sensor in a Wheatstone-bridge circuit, similar to a hot wire/film anemometer, measured h. Using fluoroscopy, we could precisely locate the steerable catheter sensor tip and sensor orientation in pigs' cardiac chambers. With flows, h varies from 2500 to 9500 W/m2 x K. With zero flow, h is approximately 2400 W/m2 x K. These values of h can be used for the finite element method modeling of radiofrequency cardiac catheter ablation.
Collapse
|
45
|
Berjano EJ, Hornero F. Thermal-Electrical Modeling for Epicardial Atrial Radiofrequency Ablation. IEEE Trans Biomed Eng 2004; 51:1348-57. [PMID: 15311819 DOI: 10.1109/tbme.2004.827545] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Epicardial radiofrequency ablation is increasingly being used for intraoperative treatment of atrial fibrillation. However, the effect of different parameters on the lesion characteristics has not been sufficiently characterized. We used a finite element model to calculate the temperature distribution in the atrial tissue under different conditions during a constant voltage radiofrequency ablation. Our simulation results show that although in the case of a thin atrium the lesion was less deep for a thin atrium, it was easier to achieve transmurality. While considering a thinner atrium, the location of the hottest point of the lesion shifted from the electrode tip to epicardial surface. This effect was due to the convective cooling of the circulating blood inside the atrium. This convective cooling phenomenon has almost negligible effects for atria thicker than 3 mm. The variability of the cooling values has no significant effect on the lesion, even for thin atria (1-2 mm). Increasing the electrode insertion depth (ID) in the tissue produced larger lesions. However, for thinner atria (thickness <2 mm), this increase in the ID reduced the lesion width. It was also proved that the presence of a fat layer between the electrode and the atrial tissue decreased significantly the lesion dimensions.
Collapse
Affiliation(s)
- Enrique J Berjano
- Departamento de Ingeniería Electrónica, Universidad Politécnica de Valencia Camino de Vera s/n, Valencia, Spain.
| | | |
Collapse
|
46
|
Tsai JZ, Will JA, Vorperian VR, Hubbard-van Stelle S, Cao H, Tungjitkusolmun S, Choy YB, Webster JG. In vitro measurement of myocardial impedivity anisotropy with a miniature rectangular tube. IEEE Trans Biomed Eng 2003; 50:528-32. [PMID: 12723067 DOI: 10.1109/tbme.2003.809475] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Due to rapid change of fiber orientation, it is difficult to measure myocardial impedivity separately in a longitudinal or transverse fiber direction without mutual influence in the two directions. Previously published values of the longitudinal and the transverse myocardial impedivity were derived indirectly from measurements that mixed the impedivity in all directions. Those values are questionable because the derivations were based on a simplified uniform myocardial fiber model. In this paper, a miniature rectangular tube was devised to facilitate direct measurement of myocardial impedivity in a uniform fiber direction. The average transverse-to-longitudinal ratio of the measured in vitro swine myocardial impedivity was about 1.66 from 1 Hz to 1 kHz and dropped to 1.25 at 1 MHz. The result is important for accurate modeling of the electrical property of myocardium in biomedical research of radio-frequency cardiac catheter ablation.
Collapse
Affiliation(s)
- Jang-Zern Tsai
- Department of Electrical Engineering, National Central University, Jung-Li, Taoyuan 32054, Taiwan
| | | | | | | | | | | | | | | |
Collapse
|
47
|
Cao H, Vorperian VR, Tungjitkusolmun S, Tsai JZ, Haemmerich D, Choy YB, Webster JG. Flow effect on lesion formation in RF cardiac catheter ablation. IEEE Trans Biomed Eng 2001; 48:425-33. [PMID: 11322530 DOI: 10.1109/10.915708] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
This study investigated the flow effect on the lesion formation during radio-frequency cardiac catheter ablation in temperature-controlled mode. The blood flow in heart chambers carries heat away from the endocardium by convection. This cooling effect requires more power from the ablation generator and causes a larger lesion. We set up a flow system to simulate the flow inside the heart chamber. We performed in vitro ablation on bovine myocardium with three different flow rates (0 L/min, 1 L/min and 3 L/min) and two target temperatures (60 degrees C and 80 degrees C). During ablation, we also recorded the temperatures inside the myocardium with a three-thermocouple temperature probe. The results show that lesion dimensions (maximum depth, maximum width and lesion volume) are larger in high flow rates (p<0.01). Also, the temperature recordings show that the tissue temperature rises faster and reaches a higher temperature under higher flow rate.
Collapse
Affiliation(s)
- H Cao
- Department of Electrical and Computer Engineering, University of Wisconsin-Madison, 53706, USA
| | | | | | | | | | | | | |
Collapse
|